German Patent Application No. DE-A-40 06 950 shows a final controlling element that is triggered by an actuating signal from a PID (proportional-plus-integral-plus-derivative) controller that becomes operational when a control program is run. The final controlling element comprises two helical gears that are in mesh, one of the gears being joined to the camshaft, and the other being driven via a chain by the crankshaft. The gears can be moved toward each other in an axial direction by means of an adjusting mechanism, so as to allow a relative torsion to result between the crankshaft and the camshaft due to the helical teeth. The adjusting mechanism is triggered by the actuating signal. This actuating signal is generated with PID action, starting out from a system deviation, i.e., from the difference between the actual angular position and a setpoint angular position. The setpoint angular position is read out from an engine characteristics map in dependence upon the prevailing operating state of the engine.
This type of PID control method adjusts relatively slowly to a new setpoint value, since the adjustment rate continually declines as the system deviation between the setpoint and actual values becomes smaller.